Hibiscus Sawfly, Atomacera Decepta HYMENOPTERA: ARGIDAE
Total Page：16
File Type：pdf, Size：1020Kb
Rose Hiskes, Diagnostician and Horticulturist Valley Laboratory The Connecticut Agricultural Experiment Station 153 Cook Hill Road, P. O Box 248 Windsor, CT 06095 Phone: (860) 683-4977 Email: [email protected] Hibiscus Sawfly, Atomacera decepta HYMENOPTERA: ARGIDAE Rose mallow, Hibiscus moscheutos, a (Figure 3). The larvae look like moth or southern native, along with related hybrids butterfly caterpillars but can be and cultivars are valued in Northeast gardens distinguished from them by the number of for their many mid- to late summer blooms short, fleshy prolegs found on the abdomen. and strong stems that rarely need staking. Moth and butterfly larvae have five or fewer Their white, pink or red flowers, some as pairs of prolegs, while sawflies have none or large as dinner plates, can have a darker eye. more than five pairs of prolegs. The Until recently, they have been relatively free hibiscus sawfly larva has six pairs of of insect and disease pests in home prolegs. Mature larvae, up to ½” long, form landscapes. In 2004 and 2005, however, straw-colored fibrous cocoons (Figure 4). larvae of the hibiscus sawfly defoliated many rose mallow plants in Connecticut Life Cycle and Damage: landscapes. This sawfly is more commonly Not much is known of the life cycle of this found in the Mid-Atlantic and Midwest pest in the Northeast. Adult activity and egg states. It also feeds on hollyhock and other laying may take place from late May through mallows. If left untreated for several the growing season until the first frost. Eggs seasons, populations can build up and kill an are laid in older leaves and hatch in about a otherwise healthy plant. week. Well-camouflaged larvae feed in groups on the undersides of leaves but leave Description: the upper epidermis intact. As they get Sawflies are close relatives of bees and larger, all leaf tissue except the veins is wasps. Hibiscus sawfly adults are dark- consumed, which gives the leaf a lacy winged, fat-waisted and 3/16” long. They appearance. With large infestations, the are entirely black with an orange spot on the accumulation of small black fecal droppings upper thorax (Figure 1). Females lay is apparent. Mature larvae form cocoons, multiple rows of six disc-like eggs in leaf often in groups, on the lower stems or in the tissue near the margins causing brown soil. With a life cycle of 28 days, multiple blisters near the leaf tip (Figure 2). Dark- generations are possible in Connecticut and headed larvae are yellowish-green with plants can be completely defoliated in a transverse rows of six or eight short, thick, matter of days. It is not known how or if black tubular glands on each body segment this sawfly passes the winter in Connecticut. ORANGESTRIPED OAKWORM ANISOTA SENATORIA, SATURNIIDAE, Rose Hiskes, The Connecticut Agricultural Experiment Station, www.ct.gov/caes 1 Hosts: the sawflies as they kill by suffocation and Larvae feed voraciously on rose mallow, disruption of the insect membranes Hibiscus moscheutos, and the hybrids of H. respectively. Do not apply foliar palustris, H. militaris, and H. lasiocarpus insecticides during bloom while bees or such as “Lord Baltimore” and “Lady hummingbirds are present. Be sure to read Baltimore”. The popular “Luna” and and follow all label directions. “Belle” series available in many garden centers are very susceptible to attack by this Cultivars that are resistant to hibiscus sawfly insect. It feeds somewhat less on hollyhock, attack may be available in the future. Three Alcea rosea. There is a hollyhock sawfly, species of hardy herbaceous hibiscus that are Neoptilia malvacearum, which may be resistant to the sawfly have been found by confused with the hibiscus sawfly. The researchers in Mississippi. Hopefully, hibiscus sawfly does not feed on woody breeders will be able to get this trait into hibiscus such as Rose of Sharon, Hibiscus horticulturally viable cultivars soon. syriacus, or the tender Hibiscus rosa- sinensis. It will feed on other ornamental mallows, as well as cotton and okra, but usually will not complete its life cycle on them. Management: As soon as leaves emerge, begin scouting the lower leaf surfaces of older leaves on susceptible plants. Handpicking larvae initially may be difficult because of their small size and how well they are camouflaged, but it is a non-chemical option Figure 1. Hibiscus sawfly adult, magnified for the small garden. Foliar sprays can be effective. In Connecticut, effective insecticides include acephate, pyrethrins, pyrethroids (eg. bifenthrin, permethrin or cyfluthrin) and spinosad. Spray must cover all infested plant parts for good control. All of these products, with the exception of spinosad, can be toxic to beneficial predatory mites and can induce secondary outbreaks of spider mites. An alternative is to use an early season soil drench of imidacloprid. This insecticide is translocated up from the roots through the Figure 2. Hibiscus sawfly egg sites, plant and will provide season-long control magnified with one application. Another alternative would be foliar applications of horticultural oil or insecticidal soap, which may be used on small larvae, but the spray must coat all HIBISCUS SAWFLY ATOMOCERA DECEPTA, ARGIDAE, Rose Hiskes, The Connecticut Agricultural Experiment Station, www.ct.gov/caes 2 References: Boyd, D. 2005. “Beating the Hibiscus Sawfly”. American Nurseryman. February 15, 2005. pp 22 – 26. Cranshaw, W. 2004. Garden Insects of North America. p. 84. Gill, S., David Clement and Ethel Dutky. Figure 3. Hibiscus sawfly larvae, magnified 1999. Pests and iseases of Herbaceous Perennials. p. 183. Tippins, H. H., 1965. “The Sawfly Atomacera decepta, a Pest of Hibiscus.” Journal of Economic Entomology. Vol. 58, p 161. Figure 4. Hibiscus sawfly cocoons, magnified HIBISCUS SAWFLY ATOMOCERA DECEPTA, ARGIDAE, Rose Hiskes, The Connecticut Agricultural Experiment Station, www.ct.gov/caes 3 .